In a silver halide color photographic material, a color image is formed by the reaction of a dye forming coupler (abbreviated as a coupler, hereinafter) with an aromatic primary amine developing agent oxidized by color development subsequent to the exposure of said material to light.
In the color image formation as described above, color reproduction is generally effected in accordance with the subtractive color process, that is, blue, green and red colors are reproduced by the image formation of yellow, magenta and cyan colors bearing complementary relationships to their respective colors. In general, a yellow color image is formed using an acylacetoamide coupler and a malondianilide coupler as yellow dye forming coupler (abbreviated as a yellow coupler, hereinafter), a magenta color image using a 5-pyrazolone coupler, a pyrazolotriazole coupler and the like as magenta coupler, and a cyan color image using a phenol coupler and a naphthol coupler as cyan coupler.
Yellow, magenta and cyan dyes to be obtained from those couplers are generally produced in silver halide emulsion layers sensitive to radiations which bear complementary relationships to the radiations absorbed by said dyes, respectively, or their respective adjacent layers.
As for the yellow couplers, acylacetamide couplers represented by benzoylacetanilide couplers and pivaroylacetanilide couplers have generally been employed, particularly for image formation. Since the former couplers exhibit great activities upon coupling with oxidized aromatic primary amine developing agents in the development step, and the yellow dyes produced therefrom have great extinction coefficients, they have mainly been used for photograph-taking color sensitive materials, which require high sensitivity, especially for color negative films, while the latter produces yellow dyes excellent in spectral absorption characteristics and fastness, so they have been used chiefly for color paper and color reversal films. On the other hand, malondianilide couplers described in French Patent 1,558,452, and U.S. Pat. Nos. 4,095,984, 4,149,886, 4,477,563 and 4,500,634 are characterized by their high coupling activities. Of these couplers, those of such a type that a coupling eliminable group is attached to the coupling active site via its nitrogen atom have been utilized as development inhibitor releasing coupler (so-called DIR coupler) owing to their particularly high coupling activities. As already well-known, DIR couplers produce such favorable effects as to improve the granularity through fine granulation of dye mottle (fine granulation of dye image), enhance the sharpness of image through edge effect, improve the color reproducibility through interlayer development inhibiting effect, and enable the control of gradation.
Since yellow dyes obtained from malondianilide couplers have relatively great molecular extinction coefficients, they have yellow densities even when used as additives for image forming couplers, that is, DIR couplers, as well as when used for image formation. Therefore, sufficient fastness is required of these color images. However, the color images obtained from malondianilide couplers are thermally unstable, so they have a serious problem in keeping quality upon storage in the dark.